When film was king, this made sense. The process of getting duplicates and distributing them back to the group was time consuming, pricey and awkward which gave rise to the gang camera cluster. What made sense in the darker ages, is anachronistic in the digital age. Talented engineers and software designers developed digital cameras, memory sticks, email, USB, flickr, photobucket, zipfiles, and ftp servers explicitly to share digital information.
Despite all these things being literally a our fingertips, we still inundate bystanders with arm-loads of cameras to take the identical shot, and I don't know why.
Whenever this situation occurs, and the accidental photog pauses due to confusion over the point and click interface, I quip something along the lines of "Too bad we don't have a vast network of high-speed computers to share this readily transferable digital information." Some people laugh, most roll their eyes, but my point stands.
If emailing or posting pictures is too much of a hassle, perhaps cameras should be able to transfer pictures between them wirelessly, so the swap can be done on the spot. iPhones can probably do this already, when not grating cheese or adjusting the blinds on the space shuttle, but once real cameras have this functionality, I hope to see an end to the gang-up camera cluster.